1. Technical Field
The present invention generally relates to touch detection technology fields and, particularly to a capacitive touch detection system and a detection signal receiving and waveform shaping module thereof.
2. Description of the Related Art
Referring to FIG. 1, which illustrates a schematic structural diagram of a conventional capacitive touch panel. The conventional capacitive touch panel generally constitutes a capacitive touch detection system cooperatively with a conventional detection control circuit (now shown), and the conventional detection control circuit generally includes a digital controller, a transmitter, a receiver, a voltage amplifier and an analog to digital (A/D) converter electrically coupled to one another in a suitable manner. As illustrated in FIG. 1, the conventional capacitive touch panel 24 includes a plurality of input terminals X1˜Xm and a plurality of output terminals Y1˜Yn. The detection control circuit generates a scanning voltage signal with particular voltage amplitude (e.g., a square waveform signal as illustrated in FIG. 1). The scanning voltage signal is then inputted into the input terminals X1˜Xm of the capacitive touch panel 24 in a double-side driving mode for scanning the whole capacitive touch panel 24. When the capacitive touch panel 24 is in operation, the capacitive touch panel 24 will output a plurality of detection voltages (i.e., generally one type of detection signals) from the respective output terminals Y1˜Yn thereof. The detection voltages are sent to the detection control circuit and then processed through the detection control circuit to be a touch detection result as output.
FIG. 2 illustrates waveforms of the detection voltages outputted from the respective output terminals Y1˜Yn of the capacitive touch panel 24. As seen from FIGS. 1 and 2, since original RC loading distribution of the capacitive touch panel 24 is uneven, the more near to the middle of the capacitive touch panel 24, the larger of the RC loading, therefore an amplitude of the detection voltage outputted from the middlemost output terminal is minimum (e.g., 70 mV) under the situation of the capacitive touch panel 24 being untouched, and in the double-side driving mode, amplitudes of the detection voltages of the left-most side and right-most side of the capacitive touch panel 24 are maximum (e.g., 380 mV and 360 mV respectively).
When a reference voltage of the analog-to-digital converter in the detection control circuit is set to be a fixed value (e.g., 3.3V), the amplified detection voltages outputted from the voltage amplifier must be lower than 3.3V so that the analog-to-digital converter can discriminate them. If the maximum detection voltage illustrated in FIG. 2 is taken to calculate the magnification of the voltage amplifier and no more than the reference voltage 3.3V of the analog-to-digital converter after being amplified, the magnification is 8. Therefore, the amplified maximum detection voltage is 3.04V and the amplified minimum detection voltage is 0.56V. Because a current absorbed by human body who touching the capacitive touch panel 24 is little, excessive large differences among the amplified detection voltages outputted from the respective output terminals Y1˜Yn under the situation of the capacitive touch panel 24 being untouched would not facilitate the digital level discrimination in the analog-to-digital converter 228.